Road vehicles are generally known and comprise a drive unit for driving the vehicle. To make it possible to operate the respective drive unit, a drive unit control device is usually provided, which is used to drive the drive unit.
Many road vehicles have an internal combustion engine as a drive unit. Modern internal combustion engines have a comparatively small size, which is manifested especially in a relatively small displacement. As a consequence, such internal combustion engines have a comparatively low noise level during operation. In conjunction with an improved muffling in the area of the engine compartment and/or in the area of a passenger compartment, passengers and especially the driver of the vehicle are often no longer able to recognize the current operating state of the internal combustion engine on the basis of an engine noise correlated therewith. Especially in connection with a start-stop system, which shuts off the internal combustion engine automatically when the vehicle is stopped, for example, at a traffic light and automatically restarts the internal combustion engine when the vehicle is then to start moving again, the driver of the vehicle is often unable to distinguish whether the internal combustion engine is operating or not. However, the driver of the vehicle needs to be able to identify the current operating state of the internal combustion engine quasi in the form of an acoustic feedback of the corresponding engine noise. Permanent awareness of the current operating state of the drive unit is of increased significance for increased driving safety and vehicle safety.
This problem is more acute in case of vehicles that have an electric motor as the drive unit, because an electric motor has an extremely low noise level compared to an internal combustion engine and generates operating noises that are entirely different from those of an internal combustion engine. The noises generated by an electric motor are often very unfamiliar for users of vehicles, which makes it considerably difficult to assess the current operating state of the drive unit. In addition, electric motors usually have a considerably lower noise level than internal combustion engines. This is also true of hybrid drives, in which the drive unit comprises both an internal combustion engine and at least one electric motor, and the internal combustion engine may be used as an additional drive or is used as a so-called “range extender” and is correspondingly used only to generate power for the electric motor in question rather for directly driving the vehicle. Thus, there is a need for providing an acoustic feedback for the driver of the vehicle for vehicles that have an electric motor as a drive unit as well in order to make it possible to better assess the current operating state of the drive unit.
However, the low-noise drive units of modern road vehicles may also become a problem for other traffic participants as well, such as other vehicle drivers, cyclists and pedestrians, because they are acoustically quasi unrecognizable against the usual background noise. In particular, pedestrians and cyclists are used to recognizing oncoming vehicles from their engine noise. This is quasi no longer possible in case of electric vehicles or in hybrid vehicles in the electric drive mode. Since it is very difficult to change habits, this implies a high risk potential, especially for pedestrians and cyclists.